The overall aim of this project is to develop an interface between organotypic brain neural circuits and electrophysiological recording equipment that is capable of long-term (weeks), highly parallel stimulation and recording of electrical activity at the level of individual cells and their processes. Our understanding of the role of individual neurons in the neural circuits of the central nervous system will benefit from the introduction of tools that allow the researcher to manipulate the circuit connectivity and monitor the electrical activity in vitro, over long term, and in a system that contains a basic functional unit of the in vivo circuit such as a cortical column or a slice of the hippocampus. We propose to develop an in vitro platform that combines organotypic brain slice cultures with a microdevice that is capable of geometric confinement of the axonal tracts connecting various parts of the circuit. The device will consist of polymer microchannels for axon guidance and an integrated microelectrode array for stimulation and recording of the signals in the neural circuit. The confinement of axons in insulated microchannels will enable parallel and independent stimulation of many axons in a pathway under study, mimicking the functionality of axonal pathways in vivo. We will focus on two model pathways, the thalamocortical pathway that can be recreated in vitro by coculturing slices from the thalamic nuclei and the primary cortices, and the perforant path, recreated by coculture of hippocampus and entorhinal cortex slices. These pathways, when recreated in vitro in a device that enables the researcher to apply stimulation selectively (to individual axons) and record from multiple cells in the recepient neural network over long term. The specific aims of this proposal are: (1) Fabrication of the interface microdevice with polymer channels for axon confinement and integrated multiple electrode array for long-term recording, (2) Organotypic cultures of perforant and thalamocortical pathways on microfabricated devices, and (3) Stimulation/recording of neural activity from model pathways. The platform developed in the course of proposed research will enable detailed investigation of the role timing-dependent synaptic plasticity plays in the development of neural circuitry, and of Hebbian learning mechanisms, contributing to understanding of the causes of developmental and learning disorders. The organotypic culture-electrode array platform also has an important application in medical research as an in vitro model for evaluation of the effects drugs, electrical stimulation, and/or cellular therapies (stem cells, etc) have on the neural circuitry, and on the growth rate, myelination, and signal conduction in the axons of the re-created pathway. [unreadable] [unreadable] [unreadable]